1. Field of the Invention
The invention relates to a separation set for blood component preparation and similar separations in a centrifuge rotor of a type comprising an annular separation compartment and a central compartment, which are arranged concentrically with the axis of rotation of the rotor and communicate with each other via an annular slot, and comprising means for reducing in operation the volume of the separation compartment. The separation set comprises a plate-like separation container of a flexible material and a first component container which by means of a tube is connected to the center of the separation container.
2. Description of the Related Art
In blood component preparation, blood is separated into the components plasma, buffy coat and red blood cells by centrifugation. A sterile set of interconnected flexible containers is used. The presently most common mode of operation is to use a sterile set of interconnected rectangular blood bags, one bag constituting the separation container, to which the blood is supplied, and the others being component containers, to which the separated components are then transferred. The entire set is centrifuged standing in swing-out centrifuge cups and, after centrifugation, the blood components form layers in the separation container according to the increasing specific weight, viz. a plasma layer, a buffy coat layer and a layer of red blood cells. Then the set of bags is removed from the centrifuge and moved to a pressing device for pressing out the plasma layer and then the buffy coat layer to associated component containers. The manual handling of the bags when the layers are in contact with each other results in a certain remixing, and it is inevitable that a certain amount of buffy coat remains in the separation container together with the red blood cells after the pressing-out operation.
Modem blood component therapy, however, requires very pure fractions of plasma and red blood cells, i.e. they should as little as possible be contaminated by the intermediate buffy coat fraction. The pressing-out of the various fractions from the separation container constitutes a critical operation with respect to the achieving of pure components.
An improvement in this respect is disclosed in WO 96/29081, where a more complete pressing-out of the buffy coat fraction is achieved by applying a pulsating pressure to the top of the container.
A different technique of achieving high purity of the separated fractions is to use a centrifuge rotor of the type mentioned by way of introduction, in which an annular separation container is compressed in the separation compartment of the rotor during rotation, and the separated layers are pressed to the central compartment of the rotor while they are affected by the prevailing G field. According to WO 87/06857, a centrifuge rotor of this type is known, and in one embodiment there is described an annular pinch means which acts in the slot-like zone between the annular separation compartment and the central compartment arranged inwardly thereof. A flexible plate-like separation container extending over the separation compartment and central compartment is divided by said pinch means into an outer annular container and an inner central container. A charge of blood is transferred to the annular part and separated by centrifugation. At a certain predetermined rotational speed, the pinch means opens the slot-like connection and at the same time the volume of the annular separation compartment decreases, whereby plasma is displaced via the central part and further on to a centrally connected plasma container, and buffy coat is displaced into the central part. Then the pinch means closes the connection. Plasma is now available in the connected plasma container, buffy coat in the central part of the separation container and red blood cells in the outer part of the separation container. The buffy coat and the red cells must, however, somehow be taken care of before the separation container can be removed from the centrifuge since the action of the pinch means ceases when the cover of the rotor is opened. This problem has not been satisfactorily solved, and therefore this centrifuge variant with the annular pinch means has not been used in practice, although it offers a very advantageous way of displacing a component layer to another container.